tack,speedo,gear indicator not working. truck has no pickup at all. on 1995 GMC 1500 Pickup

the tack,speedometer,gear indicator light dont work at all. once or twice they came back and worked and the truck ran good as always. when they are out the truck has no power at all.I got the obd1 66,65,81,82,83.65 n 66 are air cond codes n the truck had no air from factory.81 is BRAKE INPUT CIRCUT FAULT and 82 is IGNITION CONTROL(IC)3X SIGNAL ERROR.code 83 I could not find.

Asked by for the 1995 GMC 1500 Pickup